A landmark climate bill narrowly passed a key procedural hurdle in the House Friday, a sign that leadership may have the votes for final passage later in the day.

It passed by a vote of 217-205.

Passage of the controversial bill will hand Democrats and President Barack Obama a major victory on a cornerstone administration policy. It would also give Washington strong bargaining leverage ahead of international climate negotiations later this year. If it fails, therefore, it would be a major setback for Democrats.

The legislation, totaling about 1,200 pages, would require the country to reduce carbon dioxide and other greenhouse gas emissions by 17% from 2005 levels by 2020 and about 80% by the next century. U.S. carbon dioxide emissions from the burning of fossil fuels have been increasing at about 1% a year and are expected to continue to go up if no mandatory reductions are required.